As a rule, loads carried under aircraft comprise either two spaced rings or two so-called saddles. These rings or saddles are engageable by corresponding hook means of the locking system.
In devices of this character the load may be locked in position, as disclosed in the U.S. patent application Ser. No. 949,484, now U.S. Pat. No. 4,202,576, filed on Oct. 6, 1978 by the same applicants, by causing the load to engage fixed bearing points (rigid with the carrier device or the aircraft structure) through a complementary upward movement of the hook means. In contrast thereto other known propositions consist in lowering the load bearing points either through a downward movement of translation or through a rotation about fixed pivot members carried by gripper arms.
It is also possible to wedge the load in position by using wedging screws in the form of small jacks disposed at the end of fixed arms disposed on top of the load.
In fact, many devices have already been proposed up to now for carrying and wedging loads under aircraft, and all of them have various advantages and also various shortcomings.
The main advantageous features characterising the device disclosed in the above-mentioned patent application are on the one hand the equal distribution of stress among the two hook means due to the use of a rudder-bar like connecting-rod system, and on the other hand a centralized wedging control capable of acting very quickly. As already mentioned, this device is characterised by complementary simultaneous upward movements of the hook means.
However, when the upper portion of the airbone load, irrespective of its shape, must be positioned at a well-defined height in relation to the carrier device or when it is necessary to have the possibility of carrying and wedging loads having different diameters, the necessary complementary movement of the hook means is in most instances either impossible or insufficient.